Some processes of preparing optical or ophthalmic lenses start with the selection of an unfinished or semi-finished glass or plastic lens blank. Typically, a semi-finished lens blank has a finished surface and an unfinished surface.
At least one of the surfaces of the lens blank has to be adapted so as to generate the required corrective prescription.
By machining the unfinished surface of the lens blank, the required corrective prescription can be generated.
Thereafter, the surface having been machined is polished and the peripheral edge of the thus processed lens blank is provided with a final desired contour thereby establishing a finished optical or ophthalmic lens. According to other processing methods, the finished ophthalmic lens can be directly processed from a lens blank by machining both surfaces of the optical lens blank. The lens blank can be a plastic lens blank.
Reducing the time required for the machining step reduces the overall cost of the manufacturing process.
One solution for reducing the machining time consists of increasing the infeed of the machining tool during the machining process.
One of the limits of the increase of the infeed of the machining tool is the quality of the produced surface. However, the greater the radius of the machining tool, the greater the infeed of the machining tool can be increased without degrading the quality of the machined surface.
Machining tools have synthetic monocrystal diamond tips and therefore, increasing the radius of such a diamond tip, increases the volume of synthetic monocrystal diamond to the power of 2 to 3. Thus, increasing the radius of the diamond tip increases the cost of the machining tool and the machining process.
The discussion of the background herein is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was published, known or part of the common general knowledge at the priority date of any of the claims.